The field of the present invention is a drive mechanism for transmitting power from an inboard motor to a stern drive propeller.
Heretofore, there have been several different mechanisms for powering a propeller of a power boat. There are two general types of devices employed with inboard motors: a fixed propeller shaft with a rudder for steering, and a stern drive inboard-outboard with an outdrive that is articulated for steering. The latter type does not require additional steering mechanisms as the thrust from the propeller can be directed to effectively steer.
There are several patents which represent the types. of stern drives presently available. The earliest stern drive known to the inventor relevant to the present invention is Adams et al., U.S. Pat. No. 3,933,116. This patent uses an inclined shaft from an inboard motor to an outboard, articulated propeller shaft. According to the drawings in Adams et al., the motor is positioned low in the bilge and is inclined toward the stern. Patents which show the inboard motor high in the bilge include Conners et al., U.S. Pat. Nos. 4,565,532 and 4,775,342, and Weismann, U.S, Pat. No. 4,728,308. It is pointed out in the Conners et al. and Weismann patents that it is understood to be beneficial to run a boat with only 55% of the propeller submerged in water, particularly competition type boats.
It is believed beneficial to submerge the propeller relative to the keel at varying heights.
One final patent of interest is Arneson, U.S. Pat. No. 4,645,463, which is directed to a marine out drive with a universal joint connected to and rotated by a shaft of an inboard engine. One version shows the universal joint inside the boat hull where it is not exposed to salt water.
A principal difference between the existing patents and the present invention is the manner in which critical moving parts are protected from the corrosive nature of salt water. The patents cited have exposed moving parts subject to corrosion damage. In some situations the universal joints are unprotected, and in other hydraulic mechanisms for raising and lowering the propeller and its shaft are exposed.